Think twice before drenching for rumen fluke

At this time of year, many of us are submitting samples for faecal egg counts (FEC) to monitor parasite infection in our grazing livestock. 

But did you know that a positive FEC for rumen fluke is not necessarily a cause of concern and the decision to treat infected livestock should be cautiously made?

The Sustainable Control of Parasites in Sheep (SCOPS) and Control of Cattle Parasites Sustainably (COWS) groups encourage producers to monitor liver fluke in their livestock using FECs. Co-infections of liver fluke and rumen fluke are common, but liver fluke remains the more important of the two parasites. In most cases, a positive rumen fluke FEC does not indicate any production loss or the need for treatment.

Dr Bethan John, AHDB Animal Health and Welfare Scientist and COWS member explained: “Adult rumen fluke lay eggs in the rumen which are detected using FEC. However, it is a heavy burden of immature rumen fluke in the intestine which causes a livestock health and welfare issue.”

Clinical disease is associated with large infestations of immature rumen fluke, which feed on intestinal tissue and can cause poor body condition and diarrhoea. Currently, there are no diagnostic tools specifically for immature rumen fluke, and their presence is not detected with a FEC as they do not lay eggs.

Rumen fluke shares the same intermediate snail host as liver fluke. An integrated parasite control plan involves reducing pasture contamination with infective cysts in spring and reducing snail habitat on-farm in summer. During autumn, you can limit livestock exposure by fencing off snail habitats and in winter, use strategic treatment - only if clinical signs are present.

The treatment options for rumen fluke are very limited – see the AHDB Parasite Control Guide. Oxyclozanide should only be prescribed by a vet where clinical signs are evident and following a positive FEC. According to SCOPS and COWS experts, anecdotal reports of production and/or health benefits in response to rumen fluke treatment are unlikely to be due to the removal of adult rumen fluke. Such gains are more likely due to resolving a co-infection of liver fluke, which may not have been detected.